232 



THE EXTINCT BATRAC1IIA, REPTILIA 



A1VOJMODONTIA. 



Dicynodon Owen. 

 Dicynodon rosmarus Cope sp. nov. 



A species of this germs occurs in the Triassic beds of Pennsylvania, thus completing 

 the similarity between them and the Trias of S. Africa and India in the combination with 

 Labyrinthodonts (Eupelor), Thecodonts (Belodon), and Dinosauria (Clepsysaurus). The 

 species is represented by two shed canine teeth, one specimen represented by the root of the 

 fang only. They indicate one; of the larger species, the root being about nine lines in diame- 

 ter at the basis, the crown rather strongly curved. Section a wide oval, more circular near 

 the apex. Other remains, more characteristic, will shortly be described. 



From the " red bed" of Wheatley's section at the tunnel at Phcenixville, Chester Co., 

 Pa., Museum of Chas. M. Wheatley, A.M., to whom T am indebted for the loan of the 

 specimens. 



TESTUDI1ATA. 



Adocus, Cope. 



Proceed. Acad. Natl. Sciences, Phila., 1868,285. 



Character. Anterior and posterior lobes of tlio plastron abbreviated, narrowed, and not, emarginate. Eight paired 

 ■tenia] bones ; twelve eternal scuta, the numerals extending anteriorly, tbe pectorals and gulars both small. A series 

 of plates, " intermarginals " within the marginals, on tbe sternal bridge. Rib beads, i. e., tbe oapitula, wauling in 

 the species whose eostals have been examined. 



This genus was originally described with JSmys beatus Leidy from tbe Cretaceous Green Sand of New Jersey, as the 

 type, and its primary character was regarded as the absence of the costal oapitula. In the synopsis of extinct rep- 

 tilia of New Jersey, published in Pljrf. (look's Geological Survey of that State, five species were enumerated, as 

 follows: A. petrosus Cope, A.Jirmus Leidy, A. beatus Leidy. A. pramis Leidy, and A. agilin Cope. Tbe two species 

 first enumerated having subsequently been found to possess well developed costal capitula ; I referred them to Emys, 

 in the present work, p. 120. My specimens of A. agilis being at the time very imperfect, it was not described. 



At present, I propose; to point out its characters, as well as those of the other species of the genus. Two species 

 are added, the whole number being then live. One of these is from the Cretaceous deposits of Wyoming, the others 



from New Jersey. 



The plastron in this genus presents marked peculiarity. The great, reduction of the anterior and posterior lobes 

 gives it a form approximating that of StauxotypUB. The anal scuta are of large si/.e, and the femoral abdominal 

 scuta,! suture (in A. agilis) extends across just in advance of the inguinal notch. The abdominal is the widest pair 

 of scuta, in consequence of the relatively great Longitudinal extent of the bridge; their anterior outline falls a, little be- 

 hind (lie a,xilla,ry notch. The humeral scuta have a, remarkable anterior extent, so much so as to lead to the suspicion 

 thai fchej were confluent with the pectorals, or perhaps wanting. In the ca.se of A. pectoral™, having only the hyos- 

 Icinal bones, I was Induced to think that they were really the pectorals, and that the abdominals were the true 

 numerals, as is seen in the genns Plcurostcnium; the posterior position of the humerals in the latter being owing to 

 the existence of an additional pair of sternal bones. An examination of 1,1a; structure iii A. agttii, and A. wyomingen- 

 ri« dispels this view, and shows that the true pectorals are much shortened, and have an anterior position, and that 

 the gulars are also small and narrowed, the genus approaching Chelydra in these respects. 



The lateral scales of abdominal marginals is seen in the existing genera Macroohelys and Dermatemys. The 

 affinity of Adocus is to the latter, but the entire acuminate free lobes of the plastron distinguish it well. The lateral 

 marginal scuta, in A. agilis, A. icyomingensis and A. peetoralis are very distinct in our specimens, while 1 have seen it 

 in only oik; of the two or three in which the bridge is preserved in A. beatus. In A. pravus, I have not seen it, but 



